[bamfly]

1) Have jobs that pay well, and do a pretty good job of saving for years and years. There are several reasons that, despite the prominence of young founders in pop culture, successful founders in fact tend to be quite a bit older—that's one of them.

2) Family money. Either have access to it directly, or be personally "poor" but with an excellent safety net in the form of rich (-enough) relatives who won't let you really suffer if things go poorly (and may help fund your business, even). Doesn't need to be, like, Rockefeller money, either—parents who can guarantee you a place to live, comfortably cover your living expenses for a while, give you the occasional four or five figure interest-free loan without putting their financial security at risk, that kind of thing, can be enough to eliminate most of the personal risk of trying to start a business.